What's the maximum speed this mod could reach?

I don't want to sound like a troll but I wouldn't look at the maximum possible speed because chances of triggering 4x speed with a value of 6 (though some people say getting +7 speed is possible) is so low it would be like winning the lottery.
On average it could reach +8-9 speed and slightly above average but still within good probability range would be getting +11-13 speed.

Cheers